Fistulas are a major cause of morbidity and mortality, as there are over one hundred thousand cases of pathologic fistulas a year, which account for over ten thousand deaths. They cost the healthcare system billions of dollars each year to treat.
Fistulas are tissue-lined connections between body cavities and hollow organs or between such cavities or organs and the surface of the body. The fistula tract includes a void or potential void in the soft tissues extending from a primary fistula opening to a blind ending or leading to one or more secondary fistula openings, sometimes following along tissue planes of organs or between organs. Fistulas frequently develop as a consequence of infections or accompany abscess formations. Although some fistulas are purposely created for therapeutic purposes such as tracheostomy tracts, gastric feeding tube tracts, or arteriovenous fistulas for dialysis access, pathological fistulas are abnormal tracts that typically occur either congenitally or form after surgery, surgery-related complications, or trauma. They are most often open tracts that have epithelialized, endothelialized, or mucosalized.
Fistulas can form between almost any two-organ systems, or multiple organs between different sites of the same organ. For example, they may occur between internal organs and skin (enterocutaneous fistulas, gastrocutaneous fistulas, anal fistulas, rectovaginal fistulas, colocutaneous fistulas, vesiclocutaneous fistulas, intestinocutaneous fistulas, tracheocutaneous fistulas, bronchocutaneous fistulas, etc.) or between internal organs themselves (tracheal-esophageal fistulas, gastrointestinal fistulas, colovesicular fistulas, palatal fistulas, etc.). Fistulas may also form between blood vessels such as arteriovenous fistulas.
Although fistulas may form in many locations in the body, they are almost universally highly morbid to patients and difficult for clinicians to treat. For example, enterocutaneous fistulas are one of the most feared complications of abdominal surgery. Enterocutaneous fistulas are abnormal connections that form between the bowel and skin and can occur after abdominal surgery, after trauma, or as a complication of Crohn's disease. Some reports estimate that enterocutaneous fistulas may form in as many as 1% of patients that undergo major abdominal surgery. They often require months of supportive care and/or major abdominal surgery. The overall mortality rate for patients that develop enterocutaneous fistulas remains high at around 20%.
Current options for treatment of enterocutaneous fistulas include long-term conservative management or major surgery. In a first option, the patients are placed on restricted enteric intake and managed with parenteral nutritional support. The fistula leakage is controlled using a stoma bag. If the fistula output is high, drains are sometimes placed to try and control the fistula output. Spontaneous closure is relatively low at around 25%. If fistulas fail to spontaneously close with current management after 5 weeks of bowel rest, then many surgeons advocate surgical treatment at this point, though supportive care could continue indefinitely. Patients with open fistula tracts often have ongoing associated malnutrition and electrolyte imbalance issues as well as chronic non-healing abdominal wounds.
A second option is a major surgery, which has a mortality rate near 30%. The surgery involves resection of the diseased intestinal segment, extirpation of the fistula, and debridement of the fistulous tract through the abdominal wall and subcutaneous tissue. This major abdominal surgery often requires blood transfusion and post-operative ICU admissions. As a result of chronic inflammation and having abdomens that have been previously operated on, these patients typically form dense adhesions and have highly friable tissues. In addition, these patients can be severely malnourished. These conditions make operations on enterocutaneous fistulas extremely difficult and dangerous. After the surgery the patient is put on total parenteral nutrition (“TPN”) for several more days before the patient can be weaned off TPN and slowly introduced to normal foods.
Other treatment options may include implantable devices designed to aid in the closure of the fistula. These devices, however, may cause adverse immunological reactions in patients, may allow leakage of fluid around them, or may migrate or become dislodged when the patient exerts himself, such as during exercise. There is a need in the art for an implantable device for closing a fistula that reduces the chance of adverse immunological reactions, and the leakage of fluid through the fistula tract, and that has a reduced chance of migration or dislodgement during use.